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101.
102.
Granulitic lunar meteorites offer rare insights into the timing and nature of igneous,metamorphic and impact processes in the lunar crust.Accurately dating the different events recorded by these materials is very challenging,however,due to low trace element abundances(e.g.Sm,Nd,Lu,Hf),rare micrometerscale U-Th-bearing accessory minerals,and disturbed Ar-Ar systematics following a multi-stage history of shock and thermal metamorphism.Here we report on micro-baddeleyite grains in granulitic mafic breccia NWA 3163 for the first time and show that targeted microstructural analysis(electron backscatter diffraction)and nanoscale geochronology(atom probe tomography)can overcome these barriers to lunar chronology.A twinned(~90°/401)baddeleyite domain yields a ~(232)Th/~(208)Pb age of 4328 ± 309 Ma,which overlaps with a robust secondary ion mass spectrometry(SIMS)~(207)Pb/~(206)Pb age of 4308 ± 18.6 Ma and is interpreted here as the crystallization age for the igneous protolith of NWA 3163.A second microstructural domain,2μm in width,contains patchy overprinting baddeleyite and yields a Th-Pb age of 2175 ±143 Ma,interpreted as dating the last substantial impact event to affect the sample.This finding demonstrates the potential of combining microstructural characterization with nanoscale geochronology when resolving complex P-T-t histories in planetary materials,here yielding the oldest measured crystallization age for components of lunar granulite NWA 3163 and placing further constraints on the formation and evolution of lunar crust. 相似文献
103.
《Chemie der Erde / Geochemistry》2019,79(4):125519
We report on the mineralogy, petrography, and in situ oxygen isotopic composition of twenty-five ultrarefractory calcium-aluminum-rich inclusions (UR CAIs) in CM2, CR2, CH3.0, CV3.1–3.6, CO3.0–3.6, MAC 88107 (CO3.1-like), and Acfer 094 (C3.0 ungrouped) carbonaceous chondrites. The UR CAIs studied are typically small, < 100 μm in size, and contain, sometimes dominated by, Zr-, Sc-, and Y-rich minerals, including allendeite (Sc4Zr3O12), and an unnamed ((Ti,Mg,Sc,Al)3O5) mineral, davisite (CaScAlSiO6), eringaite (Ca3(Sc,Y,Ti)2Si3O12), kangite ((Sc,Ti,Al,Zr,Mg,Ca,□)2O3), lakargiite (CaZrO3), warkite (Ca2Sc6Al6O20), panguite ((Ti,Al,Sc,Mg,Zr,Ca)1.8O3), Y-rich perovskite ((Ca,Y)TiO3), tazheranite ((Zr,Ti,Ca)O2−x), thortveitite (Sc2Si2O7), zirconolite (orthorhombic CaZrTi2O7), and zirkelite (cubic CaZrTi2O7). These minerals are often associated with 50–200 nm-sized nuggets of platinum group elements. The UR CAIs occur as: (i) individual irregularly-shaped, nodular-like inclusions; (ii) constituents of unmelted refractory inclusions – amoeboid olivine aggregates (AOAs) and Fluffy Type A CAIs; (iii) relict inclusions in coarse-grained igneous CAIs (forsterite-bearing Type Bs and compact Type As); and (iv) relict inclusions in chondrules. Most UR CAIs, except for relict inclusions, are surrounded by single or multilayered Wark-Lovering rims composed of Sc-rich clinopyroxene, ±eringaite, Al-diopside, and ±forsterite. Most of UR CAIs in carbonaceous chondrites of petrologic types 2–3.0 are uniformly 16O-rich (Δ17O ∼ −23‰), except for one CH UR CAI, which is uniformly 16O-depleted (Δ 17O ∼ −5‰). Two UR CAIs in Murchison have heterogeneous Δ17O. These include: an intergrowth of corundum (∼ ‒24‰) and (Ti,Mg,Sc,Al)3O5 (∼ 0‰), and a thortveitite-bearing CAI (∼ −20 to ∼ ‒5‰); the latter apparently experienced incomplete melting during chondrule formation. In contrast, most UR CAIs in metamorphosed chondrites are isotopically heterogeneous (Δ17O ranges from ∼ −23‰ to ∼ −2‰), with Zr- and Sc-rich oxides and silicates, melilite and perovskite being 16O-depleted to various degrees relative to uniformly 16O-rich (Δ17O ∼ −23‰) hibonite, spinel, Al-diopside, and forsterite. We conclude that UR CAIs formed by evaporation/condensation, aggregation and, in some cases, melting processes in a 16O-rich gas of approximately solar composition in the CAI-forming region(s), most likely near the protoSun, and were subsequently dispersed throughout the protoplanetary disk. One of the CH UR CAIs formed in an 16O-depleted gaseous reservoir providing an evidence for large variations in Δ17O of the nebular gas in the CH CAIs-forming region. Subsequently some UR CAIs experienced oxygen isotopic exchange during melting in 16O-depleted regions of the disk, most likely during the epoch of chondrule formation. In addition, UR CAIs in metamorphosed CO and CV chondrites, and, possibly, the corundum-(Ti,Mg,Sc,Al)3O5 intergrowth in Murchison experienced O-isotope exchange with aqueous fluids on the CO, CV, and CM chondrite parent asteroids. Thus, both nebular and planetary exchange with 16O-depleted reservoirs occurred. 相似文献
104.
We report new geological, mineralogical, geochemical and geochronological data about the Katugin Ta-Nb-Y-Zr (REE) deposit, which is located in the Kalar Ridge of Eastern Siberia (the southern part of the Siberian Craton). All these data support a magmatic origin of the Katugin rare-metal deposit rather than the previously proposed metasomatic fault-related origin. Our research has proved the genetic relation between ores of the Katugin deposit and granites of the Katugin complex. We have studied granites of the eastern segment of the Eastern Katugin massif, including arfvedsonite, aegirine-arfvedsonite and aegirine granites. These granites belong to the peralkaline type. They are characterized by high alkali content (up to 11.8 wt% Na2O + K2O), extremely high iron content (FeO1/(FeO1 + MgO) = 0.96–1.00), very high content of most incompatible elements – Rb, Y, Zr, Hf, Ta, Nb, Th, U, REEs (except for Eu) and F, and low concentrations of CaO, MgO, P2O5, Ba, and Sr. They demonstrate negative and CHUR-close εNd(t) values of 0.0…−1.9. We suggest that basaltic magmas of OIB type (possibly with some the crustal contamination) represent a dominant part of the granitic source. Moreover, the fluorine-enriched fluid phases could provide an additional source of the fluorine. We conclude that most of the mineralization of the Katugin ore deposit occurred during the magmatic stage of the alkaline granitic source melt. The results of detailed mineralogical studies suggest three major types of ores in the Katugin deposit: Zr mineralization, Ta-Nb-REE mineralization and aluminum fluoride mineralization. Most of the ore minerals crystallized from the silicate melt during the magmatic stage. The accessory cryolites in granites crystallized from the magmatic silicate melt enriched in fluorine. However, cryolites in large veins and lens-like bodies crystallized in the latest stage from the fluorine enriched melt. The zircons from the ores in the aegirine-arfvedsonite granite have been dated at 2055 ± 7 Ma. This age is close to the previously published 2066 ± 6 Ma zircon age of the aegirine-arfvedsonite granites, suggesting that the formation of the Katugin rare-metal deposit is genetically related to the formation of peralkaline granites. We conclude that Katugin rare-metal granites are anorogenic. They can be related to a Paleoproterozoic (∼2.05 Ga) mantle plume. As there is no evidence of the 2.05 Ga mantle plume in other areas of southern Siberia, we suggest that the Katugin mineralization occurred on the distant allochtonous terrane, which has been accreted to Siberian Craton later. 相似文献
105.
For in situ astrobiological studies of Mars or other planets, we must employ strategies that will enable us to verify whether our approach and prototype instruments are actually capable of distinguishing life from non-life. This must be done against a background of rigorously conducted scientific characterization of the environment or sample types being considered for measurement by the instruments under development. In this study we show how a combination of mineralogical and textural features can be considered a biosignature in an early Mars analogue environment, Death Valley, California. We propose that it is a combination of features in context of the geologic matrix which allows determination of biogenicity to be made. Polymineralic microbialites (organosedimentary formations constructed by microorganisms) from a spring pool at Badwater, within Death Valley National Park, are composed of alternating biogenic and abiogenic minerals in a distinct triplet sequence related to wet and dry seasons. A microbial community, occurring as a black biofilm, produced paired layers of two different mineral types: manganese oxyhydroxides and calcite. These biogenic layers are separated from the next pair by a gypsum layer and appear to be laid down in the wet season, with the gypsum (a mineral positively identified on Mars) precipitating in the dry part of the year, abiogenically (i.e., not dependent on microbial metabolic activity for its deposition). In addition, textural features (smaller grain size and less geometric morphology) unique to the biogenic vs the abiogenic layers, were consistently observed so that texture served as a biosignature in this environment. 相似文献
106.
Condensates produced in a laboratory condensation experiment of a refractory Ca-SiO-H2-O2 vapor define four specific and predictable deep metastable eutectic calciosilica compositions. The condensed nanograins are amorphous solids, including those with the stoichiometric CaSiO3 pyroxene composition. In evolving dust-condensing astronomical environments they will be highly suitable precursors for thermally supported, dust-aging reactions whereby the condensates form more complex refractory silicates, e.g., diopside and wollastonite, and calcite and dolomite carbonates. This kinetically controlled condensation experiment shows how the aging of amorphous refractory condensates could produce the same minerals that are thought to require high-temperature equilibrium condensation. We submit that evidence for this thermal annealing of dust will be the astronomical detection of silica (amorphous or crystalline) that is the common, predicted, by-product of most of these reactions. 相似文献
107.
Amer A. Al-Rawas 《Engineering Geology》1999,53(3-4):327-350
The factors controlling the expansive nature of the soils and rocks in Northern Oman were studied. Basic geotechnical data from over 40 sites were collected and using empirical relationships, swelling potentials were identified. A laboratory testing program was carried out using undisturbed samples from these swell pressures up to 3.5 MPa, and swell percent values up to 30 were measured. The clay minerals and cations of these samples were determined and Na-smectite was identified as being the main clay-mineral present. Microfabric studies showed generally dense clay matrices. However, these swelling materials exist as impersistent bands with non-swelling soils and rocks which makes prediction of the ground heave problematic. 相似文献
108.
新疆塔里木板块西部瓦吉里塔格地区二叠纪超镁铁岩的岩石成因与岩浆源区 总被引:10,自引:15,他引:10
瓦吉里塔格地区位于塔里木板块西部,前人在此区发现了晚二叠世形成的6个爆破角砾岩筒和32条岩脉。爆破角砾岩筒属火山口相和火山管道相,脉岩属次火山相。爆破角砾岩筒由角砾和胶结物组成。角砾的主要类型是纯橄榄岩、橄榄岩、橄榄辉石岩、辉石岩等;胶结物主要是麦美奇岩和苦橄岩。据岩石化学组成和液相线橄榄石的F0分子确定的原生岩浆的MgO含量分别是18.78%和18.8%。它们的CaO/Al2O3平均值为3.9,Al2O3/TiO2平均值为2.6。这些超镁铁岩都富集LREE、大离子亲石元素和Nb、Ta,而重稀土元素贫化,并有Zr、Hf负异常。不同样品间∑REE和(La/Yb)N的差异反映了橄榄石和单斜辉石堆晶作用的影响。依据实验岩石学研究成果,熔融深度应为450km~650km。副矿物组合异常复杂,其中,刚玉的结晶深度有可能大于575km。它们的εNd(t)= 3.3~ 5.4,εSr(£)=-4.27~-10.78,^206Ph/^204Ph=18.47~22.78,^207Ph/^204Ph=15.52~15.90,^208Ph/^204Pb/38.45~39.62。Nd、Sr、Ph同位素组成与洋岛玄武岩和一些地慢柱组分相同或相近。综合各方面的研究成果可以证明,这些超镁铁岩很有可能源自于核一幔边界之上的D″层。源区本属于亏损型地幔,但在岩浆生成前不久被富含轻稀土元素和大离子亲石元素的流体交代。 相似文献
109.
Kehui Xu John D. Milliman Anchun Li J. Paul Liu Shuh-Ji Kao Shiming Wan 《Continental Shelf Research》2009,29(18):2240-2256
X-ray diffraction (XRD) mineralogical and grain-size analyses indicate that inner continental shelf sediments in the East China Sea (ECS) represent a unique mixing of clays derived from the Yangtze River and silts/sands from small western Taiwanese rivers. Taiwanese (e.g., Choshui) clays (<2 μm) display no smectite but the best illite crystallinity and are only distributed along southeastern Taiwan Strait. Both Yangtze and Taiwanese river clays are illite-dominated, but the poor illite crystallinity and the presence of smectite and kaolinite indicate that Taiwan Strait clays are mainly Yangtze-dominated. In contrast, medium silts (20–35 μm) and very fine sands (63–90 μm) in the Taiwan Strait are characterized by low feldspar/quartz, low K-feldspar/plagioclase and high kaolinite/quartz, indicating their provenance from Taiwanese rivers. Taiwanese silts and sands are introduced primarily by the way of typhoon-derived floods and transported northward by the Taiwan Warm Current during summer–fall months. Yangtze clays, in contrast, are widely dispersed southward about 1000 km to the western Taiwan Strait, transported by the China Coastal Current during winter–spring months. Since most Taiwan Strait samples were collected in May 2006, clay results in this paper might only represent the winter–spring pattern of the dispersal of Yangtze sediments. 相似文献
110.
依据《中国科技论文统计与引文分析数据库》(CSTPC),采用文献计量的方法对《矿物岩石》载文被CSTPC来源期刊的引用情况进行统计分析及评价;其所载文献质量较高,作者群的地域分布较广,已形成具有自己风格和特色且相对稳定的研究体系;在中国地质学界有一定影响,不仅是我国地质科学研究领域最重要的信息源之一。也是我国主要的地质学核心期刊。 相似文献